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b=ACL76l5Sd+BUoUsluY8/i3UoNS+cGFH3Rj0s/mLLJabx7s05Vd5XgM7k2IZwPuUZ1 vm+dE7TxcBQBL5vdfQKT7QCu2YvRtsZRw7YmrW2WTpl/F90xDo1jvphYFJA6QZi0K/ Z6MKAeYMyrITjy+f73/nzCE2a8FB+MxuU93VDKPt+9TYXQLMLGnvLbPxem8R5rD0BU Dhyuh7BwhqQL2/f401h1T0hAw3CIoYBDJpybTj3CVoISovgdWpInOnIGPmHst8b5dv eFXOAREwITIdhqk2RyLH62twitajMtKowgcAVS4WLJ5/rPsKgf0lSNHrlQf/u+CaCi vBobbffutILpw== X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200916_101441_092297_449FECA4 X-CRM114-Status: GOOD ( 15.61 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: catalin.marinas@arm.com, Leon Romanovsky , Benjamin Herrenschmidt , Bjorn Helgaas , linux-pci@vger.kernel.org, will@kernel.org, linux-arm-kernel@lists.infradead.org, Clint Sbisa Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Sep 16, 2020 at 03:09:14PM +0100, Lorenzo Pieralisi wrote: > On Wed, Sep 16, 2020 at 09:12:26AM -0300, Jason Gunthorpe wrote: > > [...] > > > > You mean the driver uses a different path to the HW which ahs that > > > overhead, not that MMIOs have that overhead right ? > > > > The different path has overhead of doing extra useless MMIOs because > > they don't combine > > For my own information, this is IB user space driver code, correct ? Yes, maybe DPDK too > It tries to mmap buffer as WC and if it succeeds write into it in an > optimized fashion (that is just pure overhead on platforms where > normal NC memory - ie WC on arm64 - does not do what the > _architecture_ defines it should). Right, pure overhead if large PCI-E TLPs are not delivered to the device. Jason _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel